*3.3. Friction Coe*ffi*cient and Abrasion Resistance of DLCs*

As shown from Table 7, DLC significantly reduces the hard alloy's friction on the aluminum alloy from 0.29–0.32 to 0.15–0.16. The effect of coating deposition on friction against steel is also noticeable, the coefficient of friction coefficient was reduced from 0.41–0.44 to 0.25–0.27.


**Table 7.** Friction coefficient of DLCs deposited on hard alloy samples.

Figure 8 shows two-dimensional optical images of wear holes on the surface of hard alloy samples after a rotating sphere is forcibly applied to them for 5 min in the presence of an abrasive suspension in the contact area. When measuring the linear dimensions (*X* and *Y*) of the section of material that has undergone abrasion, we judged the quantitative value of wear and subsequently concluded that the carbide samples are resistant to abrasion. The results shown in Figure 8 show marked differences for three types of samples: uncoated (Figure 9a), DLC-coated (Figure 9b), and (CrAlSi)N/DLC-coated (Figure 9c). There are differences in the shape of the formed wear hole and its linear dimensions. For an uncoated hard alloy sample, the worn surface area has an irregular shape with dimensions (*X* and *Y*) of 0.9 mm × 0.6 mm. For samples with DLC and (CrAlSi)N/DLCs, the worn areas have the shape of spherical recesses with dimensions of 0.6 mm × 0.55 mm and 0.4 mm × 0.4 mm, respectively.

**Figure 9.** 2D images of the worn hole on 6WH10F carbide samples after surface layer abrasion resistance tests: (**a**) uncoated; (**b**) DLC-coated; and (**c**) (CrAlSi)N/DLC-coated.
